Poly(lactic acid) (i.e. PLA) can be derived biologically from naturally occurring sources other than petroleum and is biodegradable. However, physical limitations such as brittleness and slow crystallization may prevent easy injection molding of PLA into articles that have an acceptable degree of toughness for many applications without the use of modifiers.
Manufacturers and customers that use PLA to make a variety of articles are interested in improved toughness and improved injection molding processability and cycle times for articles made from this material.
Polyoxymethylene (POM or polyacetal) is a polymer whose physical properties include excellent tribology, hardness, moderate toughness and the ability to crystallize rapidly. POM was one of the last major engineering polymers to be highly impact modified because only a few of the available rubber type materials are sufficiently compatible to disperse in the melt into sufficiently small particles that then adhere sufficiently in the solid state to allow stress transfer across the rubber-matrix interface to improve its impact resistance.
The following disclosure may be relevant to various aspects of the present invention and may be briefly summarized as follows:
WO 03/014424 discloses blends of poly(lactic acid) with polyacetal resin that may contain impact modifiers. However, compositions with further improved toughness are desirable.